1. Technical Field
The present invention relates to lasers and, in particular, to packaging for laser assemblies. Still more particularly, the present invention provides a method and apparatus for packaging a laser with a microlens and passive alignment with a molded receptacle.
2. Description of the Related Art
Fiber optics are used for short distance communications. A laser (Light Amplification by the Stimulated Emission of Radiation) is a device that creates a uniform and coherent light that is very different from an ordinary light bulb. Many lasers deliver light in an almost-perfectly parallel beam (collimated) that is very pure, approaching a single wavelength. Lasers create ultra-high-speed, miniscule pulses traveling in optical fibers. Light traveling in an optical fiber is impervious to external interference, which is a problem with electrical pulses in copper wire.
An optical fiber is a thin glass strand designed for light transmission. A single hair-thin fiber is capable of transmitting trillions of bits per second. There are two primary types of fiber. Multimode fiber is very common for short distances and has a core diameter of from 50 to 100 microns. For intercity cabling and highest speed, singlemode fiber with a core diameter of less than 10 microns is used.
A laser assembly which includes a lens and a receptacle to hold the fiber presents problems in packaging and alignment, especially for single mode fibers. The optical axes of the laser, the lens, and the receptacle must be aligned precisely to within a couple of microns for maximum coupling of light into the single mode fiber. Active alignment techniques are typically used for this, wherein the fiber is aligned while actively monitoring the amount of light coupled into fiber. Using special algorithms and precision sub-micron stages, the fiber is moved to the optimum position and then permanently fixed in place by laser welding. Post-weld shift correction is sometimes necessitated to complete the assembly. Cycle time for this entire process may be in the order of several minutes, which is very time consuming. Coupled with the high cost of the alignment and laser weld equipment, active alignment is one of the largest contributors to the overall cost of the package.
Therefore, it would be advantageous to provide a method and apparatus for allowing passive alignment of the light source to a fiber receptacle and which is also amenable to assembly using standard automated pick-and-place equipment.